WILLIAM BRANGHAM: They're still searching tonight for the man behind the latest terror attack in Turkey. He left 39 dead and nearly 70 wounded, and a claim of responsibility came today, even as police said they're getting closer to identifying the suspect.

It's the clearest look yet at the alleged gunman who attacked the Reina club early New Year's morning. Turkish officials say he rained bullets and explosives on holiday revelers. The deputy prime minister said the investigation is progressing.

NUMAN KURTULMUS, Deputy Prime Minister, Turkey (through translator): Information about the fingerprints and basic appearance of the terrorist have been found. We hope that we will find not only the terrorist, but also his connections and those who gave him support inside and outside the club.

WILLIAM BRANGHAM: Hours earlier, the Islamic State group claimed responsibility, and called the gunman a heroic soldier of the caliphate. The statement said: "The blood of Muslims that is being shed by Turkey's airstrikes and artillery shelling will turn into fire on its territories."

Turkey has been a key member of the air campaign against ISIS and has sent troops into Syria in part to fight the group. Still, Turkey's military vowed to continue strikes on Islamic State fighters. And it released new footage of air raids on ISIS positions in Syria.

Meanwhile, in Istanbul, survivors of the nightclub attack painted a more detailed picture of the mayhem that occurred early Sunday.

YOUNIS TUERQ, Survivor (through translator): As soon as he entered the club, he started firing and he didn't stop. He fired nonstop for 20 minutes at least. We thought that there were several of them because it just didn't stop.

WILLIAM BRANGHAM: The site is a popular attraction for tourists, and the majority of the victims were foreign-born. One American citizen was wounded in the attack, but returned home today.

It was the latest in a string of bloody incidents and security lapses to take place on Turkish soil. Just two weeks ago, a gunman assassinated the Russian ambassador. And, in June, three suicide bombers struck Istanbul's Ataturk Airport, killing 45 people. That attack was also blamed on ISIS.